Singleton.h

/*
 * Copyright (C) 2005-2013 by Marc Boris Duerner
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * As a special exception, you may use this file as part of a free
 * software library without restriction. Specifically, if other files
 * instantiate templates or use macros or inline functions from this
 * file, or you compile this file and link it with other files to
 * produce an executable, this file does not by itself cause the
 * resulting executable to be covered by the GNU General Public
 * License. This exception does not however invalidate any other
 * reasons why the executable file might be covered by the GNU Library
 * General Public License.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */
 
#ifndef Pt_Singleton_h
#define Pt_Singleton_h
 
#include <Pt/NonCopyable.h>
 
namespace Pt {

template <typename T>
class Singleton : public NonCopyable
{
    public:
        static T& instance()
        {
            if( !_instance )
            {
                _instance = create();
            }
 
            return *_instance;
        }
 
    protected:
        Singleton()
        { }

        ~Singleton()
        { }

        static T* create()
        {
            static T inst;
            return &inst;
        }
 
    private:
        static T* _instance;
};
 
template <typename T>
T* Singleton<T>::_instance = 0;
 
} // namespace Pt
 
#endif